Perhaps you should try some spelling variations:
"import trade integration theories." » "import trade integration theory.", "import trade integration through.", "import trade integration reforms.", "export trade integration theories.", "import price integration theories.", "import taxes integration theories."
"import trade integration efforts." » "import trade international efforts.", "import trade conservation efforts.", "export trade integration efforts.", "import price integration efforts.", "import taxes integration efforts."

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("import trade integration theories.") OR ("import trade integration efforts."))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"import trade integration theories.\") OR (\"import trade integration efforts.\"))".
• Removing quotes may allow a broader search: (( import trade integration theories. ) OR ( import trade integration efforts. )).
• Adding a wildcard symbol may retrieve word variants: (("import trade integration theories.") OR ("import trade integration efforts."))*.